Dyeing cellulose esters



Patente Sept. 7,

Robert Schnegg, gen, Germany; vested in the Alien Property Custodian No Drawing. Application May 24, 1939, Serial No. 275,399. In 1 5 Claims.

The present invention relates to the art of dyeing cellulose esters, and more especially, to a new 1: my May 28,

process for dyeing shaped articles like fibres,

films, bands, and so on of highly acetylated cellulose, i. e. cellulose acetate having an acetate content of above 59%. Such cellulose acetates are for the most part soluble in chloroform.

It is known that highly esterified cellulose acetate is not easily dyed even with such dyestuffs which are usually employed in dyeing the lower cellulose acetates. The same holds true when trying to increase the afiinity of highly esterified cellulose acetate towards other dyestuff classes, for instance, acid wool dyestuffs by animalizing. This great resistance of highly esterified cellulose acetate to all kinds of dyestuffs is presumably due to the fact that the articles manufactured therefrom possess a rather horny surface tree of pores which would allow the dyestufl particles, which are mostly high molecular, to wander into the interior.

It is known that similar difiiculties, but on a lesser scale, are encountered when dyeing contomon acetate artificial silk which is less highly esterified and is soluble, not in chloroform, but in acetone, and that it has been tried to overcome the dificulties by adding certain swelling agents to the dye-baths for such artificial sills.

However, when trying to apply the processes used in dyeing acetone-soluble acetate artificial silk to the problem in question, the result not successful. It was rather unexpected, therefore, when I'iound that articles from highly esterified cellulose acetate can be veryeasily dyed when the articles are previously brought into a high y swollen condition and are dyed in this state. in

, order toachieve this result, I have found itto be necessary to treat the articles with. at least dim, aqueous acetic acid or a swelling agent of at least equal swelling action; furthermore, it is preterable to carry out this swelling treatment at high temperatures, for instance, temperatures oi" above 50 C. It may he noted that under such conditions the common acetone-soluble artificial sill; is completely dissolved or at least destroyed to an extremely high degree. Contrary tli'ereto, the mechanical properties of esterified cellulose acetate, for instance, resistance to breaking and elongation at breaking, are practically unimpaired by the present process.

After the treatment with one of the swellin agents, the articles can be dyed directly in deep and full shades; the dyeings so obtained have good fastness properties. It is especially possible to dye animalized articles after the said swelhua' the articles of highly treatment with acid wool dyestuffs and to obtain dyeings of excellent fastness. Before dyeing, the swelling agent may be removed from the articles by washing with water, without practically losing the property of being .easily dyed. This property is only lost when thearticles are dried before dyeing.

I have now furthermore found that by a suitable treatment it is even possible to dry the articles having been treated with one of the above strong swelling agents in a manner that they retain the property of being easily dyed.- In order to achieve this result, I treat the articles which have been brought into the strongly swollen condition, if desired after removal of the swelling agent by washing, with a fixing agent selected from the group consisting of aqueous solutions of salts of organic or inorganic acids and wetting agents, which are free from sulphonic acid groups; these fixing agents may be employed alone or in admixture with each other. Apparently by this treatment the swollen condition of the cellulose acetate articles which isnecessary for their being easily dyed is fixed to some extent. After the saidfixing treatment the articles may be dried. They remain easily dyeable thereafter and may be stored for any lengthof time or shipped to the customer without being impaired with regard to their dyeing properties. If before or during dyeing the fixing agents are washed'out from the articles, the cellulose acetate will again pass into the unswollen state whereby the dyestufi particles are very strongly fixed in the interior of the material so that the dyeings produced in this way show excellent fastness properties. For instance, dyeings withacid wool dyestufis on animalized cellulose material having been produced according to my invention are faster in many respects, for instance, against iulling and washing than the same dyeings on wool. As I have mentioned in several instances, the process according to my invention is of special value in dyeinganimalized material of highly esterified cellulose acetate with acid wool dyestuffs. is produced in known manner, for instance, by incorporating basic substanceslike nitrogen bases with the material, for instance, by adding a. suitable nitrogen base to a spinning solution for artificial fibres from highly acetylated cellulose.

lit is possible in this way, for example, to prepare.

artificial fibres from cellulose having an acetic acid content of above 59% which can be dyed alone or together with wool in equal shades as wool. For example, cellulose triacetate fibres are prepared which contain a basic nitrogen contain- Such materialing resin, the fibres are treated with at least 40% aqueous acetic acid or a swelling agent of similar strength, are then treated with one of the above mentioned fixing agents and thereupon dyed with an acid wool dyestufi. The fibres may then be workedup into a mixed fabric together with wool and, by aftertreating with the same dyestufl',

may be uniformly dyed. It is self-understood that in a similar way two-colored efiects may be produced. It is furthermore possible to work up -animalized cellulose triacetate fibres together with wool to slivers, yarns, skeins, fabrics and so on, and to treat these materials with a swelling agent which will not impair the wool. Thereupon the materials may be dyed in one on the same bath in uniform shades with acid wool dyestufi's. As above mentioned the fastness of the dyeings on the cellulose acetate articles surpass that of the same dyeings on wool, especially as regards the fastness to washing and fulling.

Of course the process is also applicable to textile printing. For instance, a fabric from cellulose triacetate fibres or animalized cellulose triacetate fibres may be printed with one of the above strong swelling agents andthereupon may be dyed with a suitable dyestuff, if desired, after having been treated with one of the said fixing agents. Inboth cases dyed patterns on a white ground or vice versa may be obtained.

Example 1 Fibres which have been prepared from chloroform-soluble cellulose acetate (acetic acid con tent: 59-61%) according to a wet-spinning process are continuously passed through a bath containing 60% aqueous acetic acid. The fibres swell strongly. Thereupon the fibre bundle is deacidifled by washing with water and dyed with a water insoluble cellulose acetate dyestuif. By using, for instance, Cellit Fast Blue B (Schultz, Dyestuffs Tables, 1st suppl. vol, 1934, page 75), a deep blue shade is obtained whereas without .the said swelllng treatment the fibres remain practically unyed.

When trying to treat common acetate artificial.

silk (acetic acid content: 5455%) in the same 7 way, the fibres are completely dissolved.

Example 2 common salt, they are centrifuged and dried. After a short washing, the'fibres are dyed as usual with cellulose acetate dyestuffs, for instance, Celliton Fast Black BTN (Schultz, Dyestufl' Tables, 1st suppl. sol., 1934, page 76). Contrary to the untreated fibres, they are dyed in deep and I full shades.

The usual softening and finishing agents may be added to the salt bath.

Example 3 Instead of a salt bath as described in the foregoing example, there may be used an aqueous solution of 550 g. per litre of awetting agent '60 in. a salt bath, for instance, a 20% solution of which is free from svlphonic acid groups, for instance, a reaction product of a reactive tertiary amine with the anyhdride of a substituted succinic acid, or a condensation product of oleyl al- 5 cohol or of castor oil with an excess of ethylene oxide.

Example 4 Fibres having been subjected to a swelling treatment as described in Example 1 are aftertreated with a bath containing 2-10% of a salt and 0.05-0.5% of wetting agent which'is free of sulphonic acid groups. The results are similar to those obtained according to Examples 1-3.

Example 5 Celluloseacetate artificial silk (acetic acid content: 59%) prepared by a dry spinning process is treated in skein form for 15-120 seconds at a 1 temperature of-30 C. in a 50% aqueous acetic acid. After having been washed with water, the silk is dyed with Celliton Fast Black BTN in a deep black shade, whereas the untreated silk is hardly dyed. Of course, it is possible to include an aftertreatment of the swollen fibres as described in Examples 2-4.

- Example 6 I To a row solution of cellulose triacetate, there are added 5-15% (calculated on cellulose acetate) of a reaction product of starch benzene sulfonate with anamine as described in the application Ser. No. 180,157, filed December 16, 1937, and the solution is spun into fibres. In spite of the presence of the nitrogenous compounds, these fibres are but scarcely dyed with acid wool dyestuffs.

The fibres are then continuously passed through a bath containing 60% aqueous acetic acid at a temperature of 20 C. for 15-120 seconds, thereupon washed with water and are dyed, while still wet, with acid wool dyestufls, for instance, Amido Yellow E (Schultz, Dyestuffs Tables, vol. 1, 1931, No. 16) The deep dyeings obtained in this manner are especially distinguished by their fastness. For example, the fastness against fulling is 4-5 (Normen der Deutschen Echtheitskommission 1935), whereas a corresponding dyeing on wool has a fastness against fulling of 1-2. A series of other acid wool dyestuifs act in the same way, for instance, Quinoline Yellow (Schultz, Dyestuffs Tables, vol. I, 1931, No. 918), Brilliant Crocein B (Schultz, Dyestuff Tables, 1st suppl., 'vol., 1934, No. 539), Alizarine Rubinol R (Schultz,

Fast Violet B (Schultz, Dyestuff Tables, vol. I,

1931, N0. 974), Alizarine Direct Blue A (Schultz, Dyestufl' Tables, vol. II, 1932, page 9), Azo Acid Black 3 BL special (Schultz, Dyestufl Tables, 1st suppl. vol 1934, page 70), and so on.

Example 7 A solution of cellulose triacetate in glacial acetic acid is mixed with an animalizing agent, for instance, a reaction product of chlorinated paraflln with ethylene diamine, and is spun by the wet-spinning process; the fibres obtained therefrom are swollen in a aqueous acetic acid at 60 C. for 15 seconds washed with water, and treated for 5 minutes in a salt bath containing 5% sodium acetate, 2% ammonium thiocyanate, 2% of a finishing agent and 0.5% isododecenylsuecinic acid-diethyl amino-methyl ester. The centrifuged and dried fibre is excellently dyed by acid wool dyestuffs.

Dyestufl Tables, vol., I, 1931, No. 1210), Wool Example 8 A fibre bundle of cellulose triacetate being animalized as described in Example 6 is swollen for 30 seconds at a temperature of C. in a 65% aqueous acetic acid which contains about 2% of a chromium compound, for instance, sodium bichromate or chromium acetate and, if desired, a reduction agent like formaldehyde or glucose. The bundle is freed from acid and cut into staples. The fibres are after-treated in a salt bath (containing 8% sodium acetate, 1% Ma wetting agent free of sulfo groups and 2% of a usual preparation), dried and worked up with wool to a yarn or textile fabric. uniformly dyed with acid wool dyestuffs. pecially suitable are chromable dyestufls.

Es- The dyeings on the artificial fibres are not only of the same fastness to washing, fulling and perspiration, but are equal to the dyeings on pure wool regarding the fastness to light.

Example 9 Triacetate artificial silk containing an animalizing agent is worked up with wool in the relative proportion 1:1. The mixture is treated in a bath containing 60% aqueous acetic acid and 2% glucose for seconds at 0., centrifuged, washed and dyed in the wet state with wool dyestufis such as, for example, Anthralane Blue B (Schultz, Dyestufl Tables 1st Su pl. vol., 1934,

page 68). The dyeings obtained are uniform on both kinds of fibres. Dyeings of particular fastness are obtained by using salts of the acid sulfuric acid esters of leuco vat dyes, which also dye both kinds of fibres equally and with the same fastness properties.

Example 10 On working as described in Example 9, but inserting, after the swelling, a salt treatment, similar dyeings are obtained as those of Example 9.

Example 11 Fibres of chloroform-solublecellulose acetate produced by the dryor wet-spinning process are locally printed with 60% aqueous acetic acid, if desired, in the presenceof a thickening agent and thereupon dyed, or treated with salt and after drying dyed with cellulose acetate dyestufi's at IO-80 C. Thereby fibres are obtained which show interesting two-colour effects, because the The mixture is untreated places do not or practically not absorb the dyestuff, whereas the treated fibres absorb the same very strongly.

Example 13 A fabric prepared of cellulose triacetate fibres is printed in patterns with a paste containing 65% aqueous acetic acid, washed and dyed. or

washed, treated with a salt as described in Example 'l and then dyed. With suitable dyestufl's, for instance, with Cellit Fast Blue B, dark patterns'on awhite ground are obtained.

Example 15 A fabric of triacetate artificial silk having an animalizing agent incorporated therein is printed as described in Example 14. On dyeing with cellulose acetate dyestuffs, similar effects as in Example 14 are obtained. By dyeing with acid wool dyestuffs or with chrome dyestuffs which reserve acetate silk, coloured patterns on av white ground are obtained.

I claim:

1. A process for improving articles of cellulose acetate having an acetic acid content of at least 59 percent which comprises treating the articles with aqueous acetic acid of at least 40 per cent strength as a swelling agent, treating the swollen articles with an aqueous solution of a salt selected from the class consisting of water-soluble alkali metal and alkaline earth metal salts to fix the swollen condition of the articles, and drying the articles.

2. A process for improving articles of cellulose acetate having an acetic acid content of at least per cent which comprises treating the articles with aqueous acetic acid of at least 40 per cent strength as a swelling agent, treating the swollen articles with an aqueous solution of a salt selected from the class consisting of water-soluble alkali metal and alkaline earth metal salts to fix the swollen condition of the articles, drying the articles, and dyeing the dried articles.

3. The process as defined in claim lwherein the aqueous solution of a salt is an aqueous solution of an alkali metal halide.

4. The process as defined in claim 1 wherein the aqueous acetic acid has the strangth of about 60'per cent and wherein the aqueous solution of Y the aqueous solution of a salt is an aqueous solution of sodium acetate.

ROBERT SCI-INEGG. 

